Autostereoscopic display

ABSTRACT

An autostereoscopic display has a flat display for representing a left stereo image and a right stereo image. It also has an image separating mask having vertical periodic structures for channeling the left and right stereo images onto a left eye and a right eye of a viewer. A device for horizontally moving the image separating mask in accordance with a position of a viewer is provided. A periodicity interval of the vertical periodic structures of the image separating mask is smaller or identical to two pixels. The device for horizontally moving the image separating mask is carries out a horizontal movement that is smaller or identical to the periodicity interval, wherein upon reaching a limit of the periodicity interval the image separating mask is returned by a length of the periodicity interval.

BACKGROUND OF THE INVENTION

The invention relates to autostereoscopic displays, comprised of a flatdisplay for representing the two stereo images, an image separating maskwith vertical periodic structures for channeling the left and rightstereo images onto the left and the right eye of a viewer, and a devicefor horizontally moving the image separating mask in accordance with theposition of the viewer.

For stereoscopic representation without auxiliary means, dual channelmethods and arrangements are already known that represent the left andright stereo images on a monitor, preferably on a flat display.

With these arrangements, the two stereo images, one for the left eye andone for the right eye (referred to in the following to as left image andright image), are represented simultaneously on a flat display that isorganized like a matrix in rows and columns. For channeling the leftimage onto the left eye and the right image onto the right eye,different masks, referred to in the following as image separating masks,are used. The best known ones employ strip-shaped barriers orlenticules.

With strip-shaped barriers as image separating masks, the left image issimply blocked from the right eye and the right image is simply blockedfrom the left eye. When employing lenticules, the left image isprojected onto the left eye and the right image is projected onto theright eye.

Generally, the image separating masks act based on pixel columns, forexample, the pixel columns having an uneven number are visible only forthe left eye and the pixel columns having an even number are visibleonly to the right eye. The image separating masks are in generalperiodic arrangements of vertical strips for barriers or cylinder lensesfor lenticules that are oriented in the direction of the columns of theflat display. The periodicity distance between two neighboring pixelcolumns is referred to as pitch.

When the viewer is positioned at the predetermined position, he can viewthe stereo illustration without cross-talk. When the viewer moveslaterally, the left eye increasingly views portions of the right imageand the right eye views portions of the left image. Arrangements withpixel column separation of the stereo images have the disadvantage thatthe lateral tolerance range of the viewer is very minimal forstereoscopic viewing without cross-talk. Moreover, the viewer has only aminimal tolerance range in regard to his distance from the flat display.

Since the pixels generally are composed of three color subpixelspositioned adjacent to one another, the image separating masks can alsobe organized based on subpixels. Arrangements are known that performchanneling of the left image onto the left eye and the right image ontothe right eye by image separating masks that are organized based onsubpixels. The problem in this connection is that the pixel correlationcan no longer be maintained. For example, the green subpixel of theuneven-numbered columns is no longer projected onto the left eye butonto the right eye.

The problem can be solved by re-coding (Stereoscopic Display Device,1995, JP 07013119 A) or by a new design of the flat display (FlatStereoscopic Image Display Device and its Production, 1994, JP 6046461).

Particularly advantageous is the use of lenticules as image separatingmasks that significantly increase the lateral tolerance range forstereoscopic viewing without cross-talk, maximally to the distancebetween the eyes of the viewer.

In order to further increase the tolerance range that is free ofcross-talk, the image separating masks can be designed to horizontallytrack the position of the viewer.

Methods are known in which an image separating mask that is organizedbased on pixels horizontally tracks the position of the viewer.Depending on the lateral tolerance range of the viewer, the horizontalmovement is several pixels wide. In general, this corresponds to severalmillimeters.

Disadvantageous are the high requirements posed on the mechanical partsin order to realize the tracking action of the image separating masksthat are organized based on pixels or subpixels.

SUMMARY OF THE INVENTION

It is an object of the invention to shorten the range for the horizontalmechanical tracking action of the image separating masks withoutreducing the lateral movement tolerance range of the viewer so that themechanical parts can be designed more simply but also more robust.

This object is solved in that the periodicity interval of the verticalperiodic structures of the image separating mask is smaller or identicalto two pixels and in that the horizontal movement of the imageseparating mask by using the periodicity of the structures of the widthis smaller or identical to the periodicity interval, wherein uponreaching the periodicity limit the image separating mask is returned bya periodicity interval.

The autostereoscopic display according to the invention is characterizedin particular in that the horizontal tracking action for imageseparating masks organized based on pixels and subpixels is limited forthe lateral movement of a viewer to a range of a periodicity length ofthe image separating masks, wherein upon reaching the interval limit theimage separating mask is returned by a periodicity interval. In thisway, the required movement length of the image separating mask issignificantly reduced. The mechanical part for horizontal movement ofthe image separating mask is simplified and can be designed to be morerobust at the same time. The resulting small adjusting travel results inthat even for fast movements of the viewer a tracking action of theimage separating mask is possible.

Accordingly, the autostereoscopic displays according to the inventionare suitable, for example, in particular in the area of medicaltechnology, multimedia applications and engineering.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention is illustrated in the drawings and willbe explained in more detail in the following.

It is shown in:

FIG. 1 a schematic illustration of a known barrier arrangement in a planview, wherein the viewer is at the predetermined position;

FIG. 2 a schematic illustration of the arrangement corresponding to theillustration of Fig. 1, wherein the viewer has moved laterally and theimage separating mask has tracked the viewer;

FIG. 3 a schematic illustration of an autostereoscopic display accordingto the invention with a reduction of the horizontal movement of theimage separating mask to a periodicity length.

DESCRIPTION OF PREFERRED EMBODIMENTS

An autostereoscopic display is comprised of a flat display forrepresenting the two stereo images, an image separating mask withvertical periodic structures for channeling the left and right stereoimages onto the left eye and right eye of a viewer, a device forhorizontal movement of the image separating mask in accordance with theposition of the viewer.

In a known arrangement corresponding to the illustration of FIG. 1, theuneven numbered pixel columns A, C, E, . . . of the left stereo imageand the even numbered pixel columns B, D, F, . . . of the right stereoimage, written onto the flat display 1. The vertical opaque strips a, b,c, . . . on the image separating mask 2 positioned in front preventsthat the left eye views portions of the right image and the right eyeviews portions of the left image. When the viewer is preciselypositioned, there is no cross-talk.

When the viewer moves to the right, increasingly portions of the leftimage will become visible for the right eye and portions of the rightimage for the left eye. In this way, the stereo image is overlapped bypseudoscopic components whose depth ratios are reversed.

By a known tracking action of the image separating mask 2, thecross-talk can be prevented (illustration in FIG. 2). The imageseparating masks 2 are generally designed such that the distance betweenthe eyes matches a horizontal pixel distance of the flat display 1. Fora lateral movement tolerance range for the viewer of approximately 50cm, the image separating mask 2 would have to be moved by eight pixels;this corresponds in an 1841 TFT display with SXGA resolution to a rangeof approximately 2.25 mm. For the high precision of the positioningaction of the image separating masks 2 caused thereby, this would posesignificant requirements on the mechanical guide.

An autostereoscopic display according to the invention with reducedtracking is illustrated in principle in FIG. 3 wherein the range of thehorizontal movement is reduced. The viewer is at the same position asillustrated in FIG. 2. By employing the periodicity of the imageseparating mask 1, the range for the horizontal movement of the imageseparating mask 2 is reduced to the width of a periodicity interval. Thehorizontal movement of the image separating mask 2 by employing theperiodicity of the structures is limited to the width of a periodicityinterval. Upon reaching the interval limit, the image separating mask 2is returned by a periodicity interval by means of the device forhorizontal movement.

For the assumed lateral movement tolerance range of the viewer ofapproximately 50 cm, the horizontal movement for an 18″ TFT display withSXGA resolution is reduced to <0.6 mm.

Even more significant is a possible reduction of the movement of theimage separating mask 2 for an image separating mask 2 that is organizedbased on subpixels. The pitch here has a width of <0.2 mm.

The image separating mask 2 having opaque strips is comprised ofalternating transparent and opaque vertical strips whose width isuniform and not greater than a pixel width. The periodicity distance isapproximately two pixels wide. For the subpixel-based control, thestrips are correspondingly as wide as a subpixel and the periodicityinterval is reduced generally to ⅓.

Instead of the opaque strips, in other embodiments of the imageseparating mask 2 prisms or lenses can be used wherein their distances,the periodicity interval, is approximately twice the pixel width orsubpixel width. In the image separating masks 2 with prisms, the twoprism flanks ensure that the pixel columns positioned underneath areprojected alternatingly onto the left eye and onto the right eye bymeans of the prisms that are twice as wide. The function of a lenticularmask as an image separating mask 2 according to another embodiment issimilar. In this connection, a narrow strip of alternating pixel columnsor subpixel columns is projected onto the left eye or the right eye.

Devices for horizontal movement of an image separating mask 2 are known.This can be, for example, a known stepping motor whose rotationalmovement of the rotor is converted into translatory movement of highprecision by means of a gearbox and/or an articulation and/or aneccentric coupled to the motor. The stepping motor is in principle amulti-phase electric synchronous motor that is operated by means ofelectronic circuits in pulse mode. Upon advancing of the control by onestep, the motor carries out a rotation about a step angle. The steppingmotor operates by permanent magnet excitation or is a hybrid motor.Hybrid motors are permanent magnet excited and operate according to thereluctance principle. In another embodiment, a known translatory drivecan be used.

1. An autostereoscopic display comprising: a flat display forrepresenting a left stereo image and a right stereo image; an imageseparating mask having vertical periodic structures for channeling theleft and right stereo images onto a left eye and a right eye of aviewer; a device for horizontally moving the image separating mask inaccordance with a position of a viewer; wherein a periodicity intervalof the vertical periodic structures of the image separating mask issmaller or identical to two pixels; wherein the device for horizontallymoving the image separating mask is configured to carry out a horizontalmovement that is smaller or identical to the periodicity interval,wherein the image separating mask is returned by a length of theperiodicity interval when a limit of the periodicity interval isreached.
 2. The autostereoscopic display according to claim 1, whereinthe image separating mask comprises opaque strip-shaped areas as abarrier.
 3. The autostereoscopic display according to claim 1, whereinthe image separating mask is comprised of strip-shaped prisms.
 4. Theautostereoscopic display according to claim 1, wherein the imageseparating mask is a lenticule with cylinder lenses.
 5. Theautostereoscopic display according to claim 1, wherein the imageseparating mask is organized based on pixel columns.
 6. Theautostereoscopic display according to claim 1, wherein the imageseparating mask is organized based on subpixels.
 7. An autostereoscopicdisplay comprising: a flat display for representing a left stereo imageand a right stereo image; an image separating mask having verticalperiodic structures for channeling the left and right stereo images ontoa left eye and a right eye of a viewer; a device for horizontally movingthe image separating mask in accordance with a position of a viewer;wherein a periodicity interval of the vertical periodic structures ofthe image separating mask is smaller or identical to two pixels; whereinthe device for horizontally moving the image separating mask tracks alateral movement of an observer by carrying out a horizontal movementthat is smaller or identical to the periodicity interval, wherein theimage separating mask carries out a return movement matching a length ofthe periodicity interval when a limit of the periodicity interval isreached, and repeats said horizontal movement and said return movementas needed for tracking the lateral movement.